Fluid type switch



Dec. z5, 1951 v. w. JoNEs Y FLUID TYPE SWITCH 2 SHEETS- SHEET 1 Filed Jan. 2, 1948 An.; irl

v. w. JONES FLUID" TYPE SWITCH 2 sx-EE'rs-SHEET 2 Filed Jan. 2; 1948 INVENTOR.

w. 5 M we fm MM2. T M C WW V Patented Dec. 25, 1951 UNITED STA'IEWSv PATENT OFFICE 2,580,302" FLUID, TYPE SWITCH Vincent W. J ones,lCleveland Heights, Ohio Application January 2, 1948, Serial No. 289

12 Claims. (Cl. 2007-152) This invention relates to fluid type switches` for making and breakingl electric circuits and particularly to a mercury switch of the, general type having a body of insulating material; in the inwhich a body of mercury, or other liquid conductor, within the body'forms a bridge betweenk the electrodes for making the circuitin one po sition of the body.

Heretofore, electrical switches of the general type described have been provided, a typcal example being one such as illustrated in Uf S. Letters Patent No. 2.101,093, issued to John H. Payne on December 7. 1937.

The electrical switch elements of switches such asA described in the above patent are usually sealed so as to prevent the escape ofthe mercury therefrom and to prevent theingress of air, the general purpose of excluding air being to reduce the deleterious effects of` arci-ng caused by making and breaking contact.V Frequently, they are filled with non-oxidizing gas. However, such switch elements have limitations which reduce their iield of applicability to use with relatively small currents, for exampley` to a maximum oi-Y about amperes, at 110 volts, of alternating current, though they have proven satisfactory below this maximum.

However, they are subjectv to arcingv and when used at higher amperage currents such asv 20 to 25 amperes at 110 volts, the arcing causes rapid deterioration of such switch elements, frequenta ly heating the confined air or gases so rapidly that the switch elements are blown apart. Again, the eiects of arcing on the mercury and electrodes are such that they become useless for their intended purposes.

Furthermore, such switches are limited as to.

the position in which they can operate.

One of the principal objects of the present invention is to provide a switch of the generalA character described which is less subject to arc-v ing than the prior mercury switches and in which the deleterious effects caused by any arcing which does occur are greatly reduced or sub.- stant'fally eliminated.

Another object is to provide a switch of the general type described which may be used in any number of rotated positions about its own axis A more specific object is to provide an imY proved electrode for contactwith the mercury in such aswitch.

Other objects and advantages will become, apparent from the followingV description wherein reference is made to thedrawings in which:

Fig. 1 is a side, elevation of-a switch embodying the principles ofthe present invention;

Fig. 2, is a front elevation of; theVA switch illustrated'in Fig. 1;

Figs. 3 and 4 are sectional views of the switch illustrated in Figs. 1 and 2 and are taken on lines 3.-3 and 4-4, respectively, ofv Figs. 1 andA 2, respectively;

Fig. 5 is a perspective. viewl of the mercury switch element ofthe present invention;

Fig. 6 is a left end elevation ci the body of the switch element illustrated in Fig. 5 showing the sameA inA thel on position, part thereof being shown in section for clearness, in illustration;

Figs. '7 and 8 are sectional views taken on the lines 1 1 andA 8 8, respectively, of Fig. 6, the mercury being. shown in Fig. "I for` clearness in illustration Fig. 9 is a side elevation of a modied form of switch embodying the principles ofthe present invention;

Fig. 10 is a fragmentary sectional view taken on the line Ill-IU of Fig. 9; and

Figs. 11 and 12 are right end elevations of the switch element illustrated in Fig. 10 showing it in the on and oli positions respectively.

Referring to the drawings, a switch is shown for the purposes of illustration as mounted in the usual outlet box B such as is customarily used for household light switches.

The switch comprises generally a body I which may be of synthetic plastic or other moldable plastic material of an insulating character. The body I has secured thereto a suitable supporting strap 2 which is adapted to 'fe connected to the box B for supporting the body I in proper position therein. The body I has a transverse cylindrical bearing surface 3 in which is rotatably mounted the switch element, later to be described.

Rotatably, supported in the bearing surface 3 is a cylindrical bearing sleeve `4 of insulating material which likewise may be organic or synthetic plastic, such as cellloseacetate or acrylic resin. The sleeve" 4 has a radially extending handle 5 which may be integral therewith and which' is adapted to be swung about the axis of the'bearing surface 3 from an upper Yorf position of the switch to a lower on position. Suitable springs 'I are mounted on the strap 2at each side of the handle 5,. Each spring 'I has a curved portion 8 which is convex toward the axis of the bearing 3 in e position, t0` be encased by a cooperating lue 9 on the sleeve 4. The convex portions 8 are arranged at opposite sides of the mid-position of the handle 5 between oi and on positions, and bear against their associated lugs 9 as the sleeve 4 is rotated initially from mid-position in either direction. Thus they yieldably oppose initial movement of the sleeve partway from mid-position of the handle 5 to on and off positions and suddenly release the opposing force after a predetermined movement so that the switch will be` moved rapidly to fully on or off position by the operator.

The sleeve 4 may be constrained from radial displacement from the bearing surface 3 by making the bearing of suiiicient circumferential extent to embrace more than 180 of the sleeve, the sleeve being inserted endwise during installation. If desired, however, the bearing may be of less extent than 180 so that the sleeve is held in position by the force of the springs l.

A mercury switch element, designated generally at I0, with which the present invention is particularly concerned is generally cylindrical and is mounted in the sleeve 4 for rotation therewith. Preferably it is held firmly in the desired rotated position relative to the sleeve 4 by a press fitting engagement therewith. However, the element I can be removed from the end of the sleeve by hand pressure and reinserted in any rotated position relative to the sleeve so that the element will be in the proper operating position regardless of the angle about the axis of the surface 3 at which the strap 2 supports the body I.

Referring next to the mercury switch element I0, it comprises a body II which preferably is in the form of an open end cylinder formed of rigid insulating material, such as glass, Bakelite, synthetic resin, though porcelain with an impervious shiny or vitried surface is preferred. The body I I has partition walls I2 and I3 which are spaced apart axially of the body from each other and inwardly from the respective ends of the body so as to define end contact chambers Id and I5, respectvely, and an intermediate expansion chamber I The ends of the chambers III and I are closed by suitable electrodes I'I and I8, respectively, which are sealed to the body II. The electrodes are preferably concave on their entire inner surfaces, as illustrated so that the chambers I4 and I5 are of gradually decresent horizontal cross section from their centers to their circumferences. It has been found that soft annealed nickel is the most suitable material for the electrodes in that it has a greater conductivity than hard nickel and less adherence to mercury. Mercury tends to combine or amalgamate with most metals, particularly under the heat of an arc caused by operation of the usual mercury switches and often dissolves or removes small particles of other metal when heated and reheated by the arc, eventually breaking down the metal entirely or rendering its contact surface undesirable. No such amalgamation or deleterious effects appear to result when soft annealed nickel is used.

The partition walls I2 and I3, which are shown as parallel with each other and at'right angles to the axis of the element are provided with passages I9 and 20 respectively, the passages being eccentric to the axis of the body I I. The passages I9 and 20 extend entirely through their associated walls I2 and I3 so as to afford a passage for mercury between the chambers III, I5, and I6, when the element I0 is rotated to dispose the passages I9 and 20 below the levelof the mercury 4 contained in the chambers. On the side of the partition wall I2 exposed in the chamber I there is a concavity 2| which, as best illustrated in Fig. 7, is generally oval shaped with the major axis of its periphery disposed atan angle to a radius from the axis of the body I through the axis of the passage I9. The concavity is arranged so that its periphery surrounds the end of the pasmaximum depth.

sage I9 and so that its deepest portion is at the periphery of the end of the passage I9. A similar concavity 22 is provided in the partition wall I3 on the face exposed in the end contact chamber I5.

The expansion chamber I6 is of greater diameter than the end chambers I 4 and I5 and is preferably coaxial therewith and of greater capacity than the sum of the capacities of the chambers I4 and I5. For example, the contact chambers may be about 0.650 inch in diameter and 1%; of an inch wide at the axis and the expansion chamber may be approximately 0.725 inch in diameter and about 1A; inch Wide. In a structure of this size, the Walls I2 and I3 each may be about 1/8 of an inch thick with a concavity about 11g of an inch the passages I9 and 20 preferably are angularly positioned about 10 in advance of the vertical in the off direction when the switch is in the' on position.

The chambers are lled with mercury, indicated at 23, to a depth such that when the element I0 is rotated to dispose the passages I9 and 20- in their lowermost position, the level of the mercury is above the top of the passagesl I9 and 20 an appreciable amount. Usually this results in a mercury level just below the axis of the body il.'

In on position the mercury forms in a continuous body from one electrode to the other through the chambers I4 and I5, the passages I9 and 29 and the expansion chamber I6. As a result, when the element I 0 is in on position the passages I9 and 20 are completely blocked by the mercury and prevent any air or gases lying above the level of the mercury from passing from one chamber to the other. The chamber I6 has in its circuiti# ferential Wall a small capillary duct or vent 25 which is preferably arranged so as to be above? the level of the mercury at all times, or it may be diametrically opposite from the passages I9 and 20. The vent 24 vents the chamber I6 to the outside atmosphere and is preferably of such size that the mercury cannot run out of it under the force of gravity.

In order to prevent accidental displacement of mercury from the chamber I6 through the vent 24, as by severe shaking of the element I Ii, the54 body Il is provided with an outwardly open pe# ripheral channel 25 which is iilled with rock wool1 26 or other packing which tends to obstruct the passage of the mercury yet affords a sufficient passage for air. A retaining sleeve 21 is press fitted over the body II for retaining the packing in place in the channel 25 and suitable grooves 28 are provided on the exterior of the body II andV extend from the channel generally endwise of thel body to the end of the body I I so as to be in communication with the outside air.

The element I0 is complete in and of itself and*- may be readily replaced in the switch by press'. fitting it by hand pressure into the sleeve 4.

In` order to prevent axial displacement of the` element I0 and the sleeve 4, contacts carried byv the'body are arranged to bear against the endsl of the electrodes I1 and I8. As illustrated in ijig). 3, for example, onecontact. asl bears against' In their lowermost position.

the. electrode l-"Il and. is nxedly secured to the body I or the switch and is adapted for connect-- tion to an electric power line.v Correspondingly, acontact 3I. is connectedto thezbodyl and; bears againsttheelectrode' I8 and is adapted; for con-- nection to a power line` The contacts 30; and 31 are. preferably formed of' metal having; Sunicient springiness to press positively against the associated electrodes,l thus not only holding theV switchrelement I in position but also assuring. a rm electrical contact.

In operation, the switch body t as a whole is installed in any rotated. position desired' about the axis of the, bearing surface The sleeve 4 is installed by moving it endwise. into the bear-Y- ing surface 3: axially thereof. The handle 5 may; then be moved to the on position and while held in this position, the element Il); may be pressed into the; sleeve lV while its passages ISv and 'are disposed below the axis of the element and l degrees in advance. of the vertical through the. axis, this being all the adjustment necessary for the` switch when installed in the particular positionA desired.. Suitable indicia or graduations may be marked on the ends of the body II and sleeve t. tov assistA in indicating the proper rotated relation of the. sleeve andV body. Obviously, with this adjustment, the switch body I'can be installed in any rotated position about itsV axis throughout 360 and the element I0 installed therein for proper operation..

Due to the." large capacity of the chamber I5 relative to the chambers. I4 and I5, the switch operatesv effectively even though the horizontal axis is tilted as much as from the horizontal.

Due to the arrangement of the concavities 2t and 22, the surface tension of the mercury', or its capillary attraction to the walls I2 and I3, breaks when the periphery of the concavityA passes below the mercury surface and the mercury then starts travelling toward the passages I9 and 20 before such passages have been moved belowv the mercury level. This gives thev mercury an initial velocity toward the passages I9 and 20.

Due to the positions oi' the concavities, this, tends to cause a flow of the mercury generally upwardly toward the passages when the switch is suddenly switched to an on position. At the same time, however, it causes a pool of mercury to accumulate rapidly just beneath the passages so as to provide a large contact surface forV any mercury flowing out of the passages into the contact chambers.

On the other hand. since the chamber I6 is of; larger diameter than the contact chambers, the mercury tends to flow more rapidly down its steeper circumferential wall, and in a larger volume toward the passages I 9 and 20, when the element I5 is rotated from off to toward on" position. This, and possibly because the cham-L ber I6 is vented, causes the mercury to discharge rapidly from the expansion chamber I@ through the passages I9 and 20 with a substantial ini--v tial velocity. As a result of these elects, the mercury flows from the expansion chamber through the'passages I9 and 20 into the contact chambers an instant before the mercury in the contact chambers reaches the openings I9 and 20. Consequently, the upwardly rising stream of mercury in the contact chambersand the laterally flowing stream fromY the passages I9 s andl 20. meet just 'outside of those ends .of .the passages I3 andl 20 which are inthe Contact chambers. These streams. thus meeting at an angle.. make substantially instantancousv contact.

over aliarse; area* without surging.: Likewise, on

turning-the switch to.off position, the; contact is broken: in the contact. chamber.

Since any arcing that would occur must occurv cury level.` the expansion chamber, the air above the mercury in the latter being vented` through the vent 2.4...

While air can pass. from the. expansion chamV her to the conta-.ot4 chambers while the switch is in 'oi" position,` no appreciable introduction of fresh air appears' to result, apparently due to the fac-t that the air capacity of the expansion chamber above the` level of the mercuryv is so large that the air passingA into the contact cham.- bers therefrom is merely returned to the eX,- pansion chamber when the switch is turned to on position.

In general, it has been found that the level ofthe mercury in the expansion chamber I5' should be just below the center line of the chamber and that the electrodes always should be in contact with the mercuryL over` a substantial part of their surface. For the purposes ciY illustration, the walls I2: and I3 have been 'shown as of uniform thickness, except for the concavities, and at right. angles; to the axis, of the element I9 with the passages I9 and 29 eccenv tric to the axis of the element Ill. Obviously, in the broader aspec-tsfof the invention so far as it relates to venting, the passages may be made concentric with the axis of the element lo and the walls I2 and I3 set on a bias to the axis` of the element I0, or made thicker at. one portion than at a. diametrically opposite portion, so that in` the on position the thicker wall portions are at the bottom and consequently the chambers I4, I5, and I6 are relatively narrower at the bottom portion than at the top portion. ThusV the level of the mercury is caused to rise so that the mercury overflows the passages I 9 and 2Q when the narrowportions of the chambers are at the bottom and accommodate mercury, and is caused to lowerwhen the wider portions of theI4 chambers are disposedv in a lower position and accommodate the mercury.

In Figs., 9 through 12, there is illustrated a modified form of the switch, and particularly of the mercury switch element in which latter the bod-y is partly ofmetal sonas'to dissipate heat more rapidly, makev and break contact is made betweenbodies of mercury,l as distinguished from make and breekA contact directly between a body of mercury andthe metal of the body, and make and break contact in the heat diss-ipating expansion chamber as distinguished from make and break contact; in; the contact chambers, is assu-red.4

In this form'of the invention the body 4.5i ofthe mercury switch elementY is similar to the body H heretofore described but is made of; alu,-

minum or other metal or material having good Walls of' the cups. provide insulating partitionwalls 4l andv which divide the interior. of the body 40 into end chambers 454 and 46 and Van. isolated intermediate'expansion chamber 41.

The diameter'of the chamber 41 is preferably" slightly greater than the diameter of the chambers 45 and 46. The metal of the body 4I forms the peripheral wall of the chamber 41 and is exl posed therein for contact with the mercury of' the element. 7'

The body 4l has a minute vent 48 leading from the chamber 41 to a peripheral channel 49 which may be iilled with rockwool or other material and channels or `grooves 56 leading from ythe'v channel 49 to the atmosphere, similar in formf and function to channel 25 and grooves 28 here-1h tofore described. The body is tightly tted in'a A retaining sleeve 5l similar to the sleeve 21.-

Electrodes 53 and 54 are seal fitted into the ends of the cups 40 and 4|, respectively, and form the end walls of the end chambers 45 and 45. The electrodes are the same as the electrodes I1 and I8 heretofore .described except that their outer end walls are dished for effecting better contact with the contacts 55 and 55, the con-l tacting ends of which latter are convex toward the electrodes so asto fit the dished surfaces thereof and yieldably resist removal of the element radially from its open sided supporting bearing surface 51 of the support 5B. The body 4U, with its sleeve 5I are received endwise in a cylindrical bearing sleeve 59 having a handle 66. The body is held in nxed axial position and in any desired rotated position relative to the sleeve 59 by a set screw 6|. The open front of the bearing is bridged by a dead center leaf spring 52 which is secured to the support 58 and cooperates with, lugs 63 on the sleeve 59 to assure rotary movement of the switch element by the handle fully to on and off positions respectively.l

The partition walls 43 and 44 have passages 65 and 66 therethrough, the passages preferably being aligned with each other endwise of the body 40 and, in the on position of the switch element are preferably at their lowest level which, as illustrated in Fig. 11 may be about twenty-Eve degrees from the vertical in the off direction, and are swung upwardly aboutfty de-k grees to sixty degrees clockwise, when the element is viewed from the rightin Fig. 10, tol the position illustrated in Fig. 12 which is the off position of the element. It is'noted that the position of the handle 60 is adjustable circumferenti ally of the body 46, as described, so that the switch as a whole can be placed in any position rotated about the axis of the bearing 51 and can'- operate properlv in the selected position;

The axes of the passages E5 and 66 arel not pafallel to the axis of the body 4D but oblique thereto .so that the open end of each of the passages in the expansion chamber 41 leads thev other end thereof by a slight angle when the body is rotated from an "on to an"oiT position.

Likewise the radially outermost limits of the passages and 66 are substantially at the pe-l ripheral walls of the chambers 45 and 46, respectively, and radially inwardly slightly from the peripheral wall of the expansion chamber 41.

By this arrangement, when the switch element is rotated from "off" to on position, mercury will enter the passages 65 and 66 from the contact chambers 45 and 46 before it can enter fromthe expansion chamber 41.' At the same time, since ends of the passages 65 and 66 before any meri' cury can pass into the chamber 41 through the.` passages and by the time mercury enters the, chamber 41 the area of coverage is great enough` to assure contact of the entering mercury directly" with the mercury already present 'in the chamber 41 instead of contact by the lentering mercuryr Corre-A with the bare peripheralmetal wall. spondingly, upon rotation of the element in the yopposite direction to off position, contact' is broken in the chamber 41 between mercury/cov# ering the peripheral wall and mercury returning to the chambers 45' and 46 through the passages.,

Thus there is never any make or break of contact between mercury and the metal of the body but only between portions of the mercury which.'

are always in contact with the body and elec-'- trodes, respectively.

'It is desirablejthat the contact'of the mercury entering the chamber 41 be made with that already in the chamber 41 instantaneously over a large area and with a considerable volume." To l 16 in Fig. 1l. Thus, in Fig. 1l, before the open end of the passage 66 reaches the mercury level, i

mercury has accumulated in the depression 68 closely adjacent thereto sufficient in amount sof that upon continued movement toward on po' sition it is suddenly released and completely lls theA open end of the passage 66, blocking the same against passage of air, and continues as a mass completely filling the passage and presenting initially in the chamber 41 a solid column of mer- I cury of the full diameter of the passage 66 for" making contact. Upon return toward oi" position it provides a readily available spaceto ac commodate mercury so that contact is not apt to be broken between the mercury in the chamber 45 and that in the passage before the contact is 4broken in the expansion chamber 41.

Thus mercury to mercury making of contact in the expansion chamber is assured, and since any gases in expansion chamber can escape readily and the heat generated can be absorbedand then -dissipatedv readily by metal to metal conduction,

oxidation and deterioration of the mercury and metal of the switch is negligible.

Having thus described my invention, I claimv 1. A vmercury switch element comprising a fhollow body having contact chambers therein and an expansion chamber therebetween', elec:v trodes in the contact chambers, respectively, mercury in all of said chambers, saidbody `having passage means'connecting the contact cham- 65 bers with each other through the expansion chamthe volume of 'mercury'i'n' the' expansion cl'lamfl ber is not temporarily 'reduced due to a' portion entering the passages, the peripheral wall of the chamber 41 is covered with mercury adjacent the ber,'sai'd contact chambers being sealed except for said passage means, said chambers and pas-I sage means and volume of mercury being related so as to cause mercury to connect the electrodes Atogether and block the passage means in one' position of the body andto disconnect the elec# tr'odes' from' leachiotlfierand unblock the passage means in another position of the-body', and said .body'having a vent independent ofthe passage lmeans 'and opening at one end directly into .the

expansion chamber and connecting the expansion chamber with the atmosphere above the level of the mercury in the position of the body in which the passage means are blocked.

2. A mercury switch element according to claim 1 characterized in that the air vent is continuously open.

3. A mercury switch element according to claim 1 characterized in that said vent is a capillary passage through which the mercury will not flow out of the expansion chamber under the force of gravity.

4. A mercury switch element comprising tubular body, electrodes sealed in end portions thereof and insulated from each other thereby, a pair of partition walls dividing the body into end contact chambers and an intermediate expansion chamber, said walls each having a passage therethrough, mercury in said chambers, the passages and chambers being related so that the mercury is below the level of the passages when the body is in one rotated position about its axis and is above the top of the passages when the body is in another rotated position about its axis, and said intermediate expansion chamber being of larger diameter than the end chambers.

5. In an electric switch, a supporting body having an arcuate bearing surface therein, a sleeve tting said surface and supported thereby for rotation about the axis of the sleeve, a generally cylindrical contact making and breaking mercury switch element adapted to make and break contact upon rotation about its axis to different positions, said switch element being adapted to t snugly into the sleeve in coaxial relation therewith and for rotation therewith in a plurality of relatively rotated positions of the element and sleeve about the sleeve axis, said switch element being removably accommodated in and supported by the sleeve in coaxial relation therewith and for rotation therewith, means operatively connected to the sleeve for rotating the sleeve in opposite directions, and contacts carried by the body and in electrical contact with the said contact surfaces, respectively.

6. A mercury switch element comprising a tubular body, electrodes sealing the ends of the body, partition walls in and spaced apart from each other and from the ends of the body and dividing the body interior into end contact chambers and an intermediate expansion chamber, said end chambers being insulated from each other, each partition wall having a passage therethrough in eccentric relation to the axis of the body, mercury in said chambers, the chambers, passages and amount of mercury being so related that the mercury is sufficient to fill the chambers above the level of the passages when the body is in a. horizontal position with the passages disposed in a lower position and insucient to reach up to the level of the bottom of the passages when the body has been rotated to dispose the passages a predetermined distance above said lower position, and said body having a continuously open vent independent of said passages and opening at one end directly into the expansion chamber and connecting the expansion chamber with the'tmcsphere above the level of the mercury in the position of the body in which the passages are blocked.

7. A mercury switch element comprising a tubular body, electrodes sealing the ends of the body, partition walls in the body `and spaced apart from each other and from the ends of the body and dividing the body interior into end contact chambers and an intermediate expansion chamber, said end chambers being insulated from each other, each partition Wall having a passage therethrough in eccentric relation to the axis of the body, mercury in said chambers, the chambers, passages and amount of mercury being such that the mercury is suiiicient to iill the chambers above the level of the passages when the body is in a horizontal position with the passages disposed at a lower position and insuii'icient to reach up to the level of the bottom of the passages when the body has been rotated to dispose the passages a predetermined distance above said lower position, and each of said partition walls having, in the face exposed in its associated end contact chamber, a concavity adjacent its passage and wider radially of the face than its passage.

8. The switch element according to claim 7 characterized in that said concavity is of greater area than the end of the adjacent passage and slopes from all points of its periphery toward said adjacent passage. 4

9. The switch element according to claim 7 characterized in that the concavity entirely surrounds the end of the adjacent passage.

10. The switch element according to claim 7 characterized in that the passage opens into the deepest part of the concavity.

11. The mercury switch element according to claim 9 characterized in that the concavity is oval shaped and the major axis of the periphery of the concavity is disposed at an angle to a radius from the axis of the wall through the center of the passage.

12. A mercury switch element comprising tubular body, electrodes sealed in end portions thereof and insulated from each other thereby, a pair of partition walls dividing the body into end contact chambers and an intermediate expansion chamber, said walls each having a passage therethrough, mercury in said chambers, the passages and chambers being related so that the mercury is below the level of the passages when the body is in one rotated position about its axis and is above the top of the passages when the body is in another rotated position about its axis, said intermediate expansion chamber being of larger diameter than the end chambers, and said body having a continuously open vent independent of said passages and opening at one end directly into the expansion chamber and connecting the expansion chamber with the atmosphere above the level of the mercury, in the position of the body in which the passages are blocked.

VINCENT W. JONES.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,501,906 Hybinette July 22, 1924 1,688,217 Whalen Oct. 16, 1928 1,726,426 Disteli Aug. 27, 1929 1,750,298 Corbette Mar. 11, 1930 1,762,213 Callahan June 10, 1930 2,073,529 Sambleson Mar. 9, 1937 2,101,093 Payne Dec. 7, 1937 2,260,754 Mattern Oct. 28, 1941 2,458,927 Beck Jan. 11, 1949 FOREIGN PATENTS Number Country Date 466,257 Great Britain May 25, 1937 

